1. Field of the Invention
The present invention relates generally to computer vision systems, and more particularly, to a system and method for tracking and camera calibration in a mobile computing system using coded visual markers.
2. Description of the Related Art
In certain real-time mobile computing applications, it is crucial to precisely track the motion and obtain the pose (i.e., position and orientation) of a user in real-time, also known as localization. There are several methods currently available to carry out the localization. For example, in augmented reality (AR) applications, magnetic or/and inertia trackers have been employed. However, it is not unusual that the performance of magnetic and inertia trackers are limited by their own characteristics. For example, the magnetic trackers are affected by the interference of nearby metal structures and the currently available inertia trackers can only be used to obtain information on orientation and are usually not very accurate in tracking very slow rotations. Additionally, infrared trackers have been employed but these devices usually require the whole working area or environment to be densely covered with infrared sources or reflectors, thus making them not suitable for a very large working environment.
Vision-based tracking methods have been used with limited success in many applications for motion tracking and camera calibration. Ideally, people should be able to track the motion or locate an object of interest based only on the natural features of captured scenes, i.e., viewed scenes, of the environment. Despite the dramatic progress of computer hardware in the last decade and a large effort to develop adequate tracking methods, there is still not a versatile vision-based tracking method available. Therefore, in controlled environments, such as large industrial sites, marker-based tracking is the preferred method of choice.
Current developments of computer vision-based applications are making use of the latest advances in computer hardware and information technology (IT). One such development is to combine mobile computing and augmented reality technology to develop systems for localization and navigation guidance, data navigation, maintenance assistance, and system reconstruction in an industrial site. In these applications, a user is equipped with a mobile computer. In order to guide the user to navigate through the complex industrial site, a camera is attached to the mobile computer to track and locate the user in real-time via a marker-based tracking system. The localization information then can be used for database access and to produce immersive AR views.
To be used for real-time motion tracking and camera calibration in the applications described above, the markers of a marker-based tracking system need to have the following characteristics: (1) sufficient number of codes available for identification of distinct markers; (2) methods available for marker detection and decoding in real-time; and (3) robust detection and decoding under varying illumination conditions, which ensures the applicability of the marker in various environments.